Abstract: F29.00007 : Role of wall-attached structures in the interface of the quiescent core region in turbulent pipe flow*

Authors:

Jongmin Yang(Korea Adv Inst of Sci & Tech)

Jinyul Hwang(Korea Adv Inst of Sci & Tech)

Hyung Jin Sung(Korea Adv Inst of Sci & Tech)

The effects of low- and high-speed structures on the interface of the
quiescent core region are explored using direct numerical simulation data of
turbulent pipe flow. The quiescent core region is a uniform momentum zone
located at the center of the pipe flow, which contains the highest
streamwise momentum with a low level of turbulence. The interface of the
quiescent core region can be identified from the probability density
function of the streamwise modal velocity. In the vicinity of the interface
of the quiescent core region, the streamwise velocity changes abruptly. The
abrupt jump in velocity causes an increase of the velocity gradient. The
interface of the quiescent core region is similar to the laminar superlayer
in turbulent/non-turbulent interface. The interface of the quiescent core
region contains the low- and high-speed structures. They can be classified
into wall-attached and detached structures depending on the distance between
the structures and the wall. The influence of the detached structures
accounted for most of the number of detected structures is negligible due to
its small volume. Conversely, the wall-attached structures adjacent to the
interface have a huge influence on the statistical amount of the interface,
such as entrainment characteristics.

*This work was supported by the Creative Research Initiatives (No. 2017-013369) program of the National Research Foundation of Korea (MSIP).

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2017.DFD.F29.7